This invention relates generally to vehicular vision systems and, more particularly, to a vehicular vision system which is operable to determine a distance from the vehicle to an object or light source remote from the vehicle. More particularly, the present invention is directed to determining the distance to an object whose image is captured by an image capture device. One application for the imaging system of the present invention is with a vehicle headlamp control and may identify particular light sources of interest and adjust a vehicle""s headlamps according to the distance between the vehicle and the particular light sources.
Vehicle camera or vision systems have been proposed for various applications, such as rear and/or side view vision systems, back up aids, collision avoidance systems, rain sensor systems, head lamp control systems and the like. These systems may include a camera or sensor positioned on the vehicle for capturing an image of a scene exteriorly of the vehicle. The vision systems may also include a display for displaying a captured image, or may control an associated accessory on the vehicle, such as windshield wipers, headlamps or even the brake system in response to one or more characteristics of the captured image. In some applications, it has been recognized that distance information between the vehicle and an object in the captured scene may be helpful. In such applications, a ranging device may also be included to provide this information. Various ranging devices have been proposed, such as radar, ultrasonic, sonar, infrared beam/detector devices or similar proximity sensing devices. While such devices provide distance information to the associated vehicular system, this requires an additional sensing device separate from the vehicular vision or camera system, which adds to the bulk and costs associated with the system.
One vehicle system which distance information may be particularly useful is a vehicle headlamp control system for adjusting a vehicle headlamp in response to a detection of oncoming headlamps or leading taillights associated with other vehicles. To date, there have been many proposed headlight dimmer control systems. Many of the prior attempts at vehicle headlight dimming controls include a single light sensor which integrates light from a scene remote from the vehicle. The vehicle headlights are then dimmed when the integrated light exceeds a predetermined threshold. However, these systems typically require a sufficiently low threshold of detection such that many other lower intensity light sources may also be interpreted as headlights or taillights. These systems also have difficulties in reliably detecting taillights of other vehicles traveling ahead of the operative vehicle, since the intensity of taillights is typically substantially less than the intensity of oncoming headlights.
Other proposed headlight dimming controls implement an imaging array sensor which not only senses the light originating from both headlights and taillights, but may further determine the color and intensity of the light, thereby further determining whether the light source is a headlight or a taillight. Such systems are deficient in determining the distance between the sensed light source and the subject vehicle, which would be helpful modulating the headlamps in response to both the sensed light and the distance to the light. One proposed solution is to estimate the distance between the vehicle and the light source in response to the brightness or intensity of the sensed light source, since the detected signal from the light source may at times vary with the square of the distance to the light source. However, such a calculation is only accurate when the sensed light source intensity is within a predetermined level corresponding to a known or assumed intensity of headlamps and is at certain distances. Because the intensity of headlamps and taillamps vary between vehicles and may further vary as the headlamps are modulated between high and low beams and as the brake lights are activated or deactivated, such an estimation of distance may be inaccurate in many cases.
The present invention provides a vehicular imaging system which is capable of accurately determining the distance from the subject vehicle to an object or light source sensed by the sensors of the imaging system. The distance sensor accurately estimates the distance between the sensed object and the vehicle, while avoiding excessive additional costs and bulk to the vehicle vision and/or control system. In one aspect, the present invention is intended to provide a vehicular headlamp control system which senses oncoming headlights and leading taillights of other vehicles and controls the headlamps of the subject vehicle in response to the sensed light sources and the distance between the vehicle and the sensed light sources. The control system preferably includes ranging capability for determining the distance between the sensed objects and the vehicle. The device preferably is adaptable for use in other vehicular imaging systems associated with the vehicle which may display a distance readout to an operator of the vehicle or may control a vehicle accessory in response to the distance.
According to an aspect of the present invention, a vehicular imaging system comprises at least one imaging array sensor and a control. The imaging sensor is mounted at a vehicle and has stereoscopic distance-sensing capability. The control is responsive to an output of the imaging array sensor in order to capture an image of at least one object external of the vehicle and determine a distance between the imaging array sensor and the object.
Preferably, the imaging array sensor receives a stereoscopic image of a scene remote from the imaging array sensor. The stereoscopic image includes a first image of an object in the scene on a first portion of the imaging array sensor and a second image of the object on a second portion of the imaging array sensor. The control is responsive to the imaging array sensor in order to determine a distance between the imaging array sensor and the object.
In one form, the vehicular imaging system is implemented in a vehicular headlamp control system, such that the headlamps are modulated between high and low beams in response to the distance between the sensed object or light source, which may be representative of an oncoming headlight or leading taillight, and the imaging array sensor.
In another form, the vehicular imaging system includes first and second imaging array sensors such that the first image of the object is received by the first imaging array sensor and the second image of the object is received by the second imaging array sensor. Preferably, a first and second optic element is included along the respective optic paths between the first and second imaging array sensors and the scene. The distance between the object and the sensors may then be determined as a function of a relative position of the image of the object as received on the first and second imaging array sensors and the focal lengths of the first and second optic elements.
According to another aspect of the present invention, a vehicular headlamp control for modulating a headlamp of a vehicle comprises at least one imaging array sensor adaptable to receive a stereoscopic image of a scene remote from the vehicle and a control responsive to the imaging array sensor. The imaging array sensor receives a plurality of images associated with a plurality of light sources associated with the scene. The control identifies light sources of interest and provides a control output to the vehicle. The control calculates a distance between at least one of the light sources and the imaging array sensor and provides the control output in response to the distance. The headlamp control modulates the headlamps of the vehicle in response to the control output.
According to another aspect of the present invention, a rearview vision system for a vehicle comprises at least one imaging array sensor and a control. The imaging array sensor is positioned on the vehicle and is directed outwardly from the vehicle. The imaging array sensor has stereoscopic distance-sensing capability. The control is operable to determine a distance from at least one object exteriorly of the vehicle in response to an output of the imaging array sensor.
These and other objects, advantages, purposes and features of this invention will become apparent upon review of the following specification in conjunction with the drawings.